NX40 Hardware Design
This page provides hardware design guidance for using the NX40 Series BLE module in a host board or custom embedded product.
The NX40 Series is based on the nRF52840 platform and is intended for Bluetooth Low Energy and 2.4 GHz embedded applications.
This page focuses on board-level hardware design. First bring-up is covered in NX40 Quick Start, and antenna layout is covered in NX40 Antenna Design.
Hardware Design Flow
Use this flow before finalizing the host PCB.
| Step | Design Area | Goal |
|---|---|---|
| 1 | Power input | Provide a stable power rail for the module |
| 2 | Ground | Connect all required ground pads to a solid ground reference |
| 3 | Decoupling | Place bypass capacitors close to power pins |
| 4 | Clock / crystal | Confirm crystal and clock circuit according to the reference design |
| 5 | Programming / debug | Keep SWD access available |
| 6 | Reset | Provide a reliable reset path |
| 7 | GPIO planning | Confirm pin usage before PCB finalization |
| 8 | Antenna area | Reserve antenna keep-out or RF path area |
| 9 | Test points | Add bring-up and production test access |
| 10 | Prototype validation | Verify power, firmware, and BLE operation on real hardware |
Main Hardware Blocks
| Block | Purpose |
|---|---|
| nRF52840 SoC | Main wireless MCU platform |
| External Flash | Optional storage depending on model variant |
| 32 MHz crystal | Main clock source |
| Power supply | Provides stable operating power to the module |
| Decoupling capacitors | Stabilize the supply near active circuits |
| SWD interface | Firmware programming and debugging |
| Reset | Board recovery and debug control |
| GPIO / peripherals | Application interface and host connection |
| Antenna / RF network | 2.4 GHz wireless communication path |
Power Design
The power design must follow the final NX40 schematic and datasheet.
Before powering the first prototype, confirm:
| Item | Design Check |
|---|---|
| Power rail | Correct voltage range for the NX40 hardware revision |
| Power stability | No large voltage drop during boot or radio activity |
| Decoupling | Capacitors placed close to power pins |
| Ground return | Short and low-impedance return path |
| Current limit | Use current-limited supply during first bring-up |
| Test point | Add a power test point for measurement |
Do not assume the NX15 power range applies to NX40. Confirm the final NX40 power requirement from the NX40 schematic or datasheet before production.
Ground Design
A stable ground design is important for both digital operation and RF performance.
| Rule | Recommendation |
|---|---|
| Connect all required GND pads | Do not leave ground pads floating |
| Use a solid ground plane | Keep the return path short and continuous |
| Avoid ground breaks under RF area | Prevent unstable RF behavior |
| Add ground vias | Use vias near RF and high-speed return paths |
| Keep debug ground close | Place GND near SWD/debug access points |
For wireless modules, ground is part of the RF system. Poor ground layout can cause weak signal, unstable current measurement, or inconsistent wireless performance.
Programming and Debugging
NX40 hardware should keep SWD access available for firmware flashing, debugging, recovery, and production programming.
| Signal | Purpose | Recommendation |
|---|---|---|
| SWDIO | Programming/debug data | Route to header or test pad |
| SWDCLK | Programming/debug clock | Route to header or test pad |
| GND | Debug reference | Place close to SWD signals |
| RESET / NRESET | Reset and recovery | Route to header, button, or test pad |
| Target voltage reference | Debugger voltage detection | Add if required by the debugger |
Even if the final product does not expose a debug connector, test pads are recommended for development and production support.
Reset Design
A reset path should be available for board recovery and firmware development.
| Item | Recommendation |
|---|---|
| Reset access | Route reset to a button, connector, or test pad |
| Debug support | Make reset available near SWD pins |
| Production support | Keep reset accessible during programming |
| Noise protection | Avoid routing reset near noisy switching signals |
Clock and External Flash
The NX40i32 BOM includes a 32 MHz crystal and an external SPI Flash device. These circuits should follow the reference design.
| Area | Design Note |
|---|---|
| 32 MHz crystal | Keep crystal traces short and follow recommended layout |
| Crystal capacitors | Use the confirmed values from the NX40 schematic/BOM |
| External Flash | Match firmware configuration to the mounted Flash option |
| Flash routing | Keep SPI/QSPI-related traces clean and compact |
| No-Flash models | Confirm firmware configuration before using Flash-related pins |
If your design uses an NX40 model without external Flash, make sure the firmware and pin usage do not assume that external Flash is present.
GPIO and Peripheral Planning
NX40 GPIO and peripheral routing should be planned together with firmware pin configuration.
| Interface / Function | Typical Use |
|---|---|
| UART | Host communication or log output |
| SPI | External sensors, Flash, or peripherals |
| I2C | Low-speed sensors and configuration devices |
| PWM | LED, buzzer, or control output |
| ADC | Analog sensor input |
| GPIO | Buttons, interrupts, enable pins, status signals |
| SWD | Programming and debugging |
Do not finalize GPIO routing before checking the firmware board configuration and model variant.
Test Points
Add test points for bring-up and production validation.
| Test Point | Purpose |
|---|---|
| Power rail | Voltage measurement |
| GND | Measurement reference |
| SWDIO | Programming/debug |
| SWDCLK | Programming/debug |
| RESET / NRESET | Recovery and reset control |
| UART TX/RX | Optional serial log |
| Key GPIO | Application-specific validation |
First Hardware Bring-up Checklist
Before flashing firmware:
| Check | Status |
|---|---|
| Correct NX40 variant mounted | ☐ |
| Power rail verified | ☐ |
| Ground continuity checked | ☐ |
| No VDD-to-GND short | ☐ |
| Decoupling capacitors installed | ☐ |
| SWDIO / SWDCLK accessible | ☐ |
| Reset path accessible | ☐ |
| External Flash option matches firmware | ☐ |
| Antenna layout reviewed | ☐ |
| Current limit set for first power-on | ☐ |
What Not to Include Here
To avoid duplicated content, these topics are handled in other pages:
| Topic | Go To |
|---|---|
| First bring-up steps | NX40 Quick Start |
| Chip antenna / u.FL antenna layout | NX40 Antenna Design |
| Sleep and average current optimization | NX40 Low Power Guide |
| BLE advertising and GATT | NX40 BLE Application Guide |
| Model selection and module-only integration | NX40 Module Integration pages |